Fast Chargeer. BQ2004E Datasheet
➤ Fast charge and conditioning of
nickel cadmium or nickel-metal
➤ Hysteretic PWM switch-mode
current regulation or gated con-
trol of an external regulator
➤ Easily integrated into systems or
used as a stand-alone charger
➤ Pre-charge qualification of tem-
perature and voltage
➤ Configurable, direct LED outputs
display battery and charge status
➤ Fast-charge termination by ∆ tem-
perature/∆ time, peak volume de-
tection, -∆V, maximum voltage,
maximum temperature, and maxi-
➤ Optional top-off charge and
pulsed current maintenance
➤ Logic-level controlled low-power
mode (< 5µA standby current)
The bq2004E and bq2004H Fast
Charge ICs provide comprehensive
fast charge control functions together
with high-speed switching power con-
trol circuitry on a monolithic CMOS
Integration of closed-loop current
control circuitry allows the bq2004
to be the basis of a cost-effective so-
lution for stand-alone and system-
integrated chargers for batteries of
one or more cells.
charge allows bq2004E/H-based charg-
ers to support battery conditioning
and capacity determination.
High-efficiency power conversion is
accomplished using the bq2004E/H as
a hysteretic PWM controller for
switch-mode regulation of the charg-
ing current. The bq2004E/H may al-
ternatively be used to gate an exter-
nally regulated charging current.
Fast charge may begin on application
of the charging supply, replacement
of the battery, or switch depression.
For safety, fast charge is inhibited
unless/until the battery tempera-
ture and voltage are within config-
Temperature, voltage, and time are
monitored throughout fast charge.
Fast charge is terminated by any of
n Rate of temperature rise
n Peak voltage detection (PVD)
n Negative delta voltage (-∆V)
n Maximum voltage
n Maximum temperature
n Maximum time
After fast charge, optional top-off
and pulsed current maintenance
phases with appropriate display
mode selections are available.
The bq2004H differs from the
bq2004E only in that fast charge,
hold-off, and top-off time units have
been scaled up by a factor of two,
and the bq2004H provides different
display selections. Timing differ-
ences between the two ICs are illus-
trated in Table 1. Display differ-
ences are shown in Table 2.
16-Pin Narrow DIP
or Narrow SOIC
Timer mode select 1
Timer mode select 2
Sense resistor input
Charge status output 1
Charge status output 2
5.0V ± 10% power
Charge current control
Charge inhibit input
SLUS081A - APRIL 2005
Discharge-before-charge control input
The DCMD input controls the conditions
that enable discharge-before-charge. DCMD
is pulled up internally. A negative-going
pulse on DCMD initiates a discharge to end-
of-discharge voltage (EDV) on the BAT pin,
followed by a new charge cycle start. Tying
DCMD to ground enables automatic
discharge-before-charge on every new charge
Display select input
This three-state input configures the charge
status display mode of the LED1 and LED2 out-
puts and can be used to disable top-off and
pulsed-trickle. See Table 2.
Voltage termination select input
This three-state input controls the voltage-
termination technique used by the
bq2004E/H. When high, PVD is active.
When floating, -∆V is used. When pulled low,
both PVD and -∆V are disabled.
Timer mode inputs
TM1 and TM2 are three-state inputs that
configure the fast charge safety timer, voltage
termination hold-off time, “top-off”, and
trickle charge control. See Table 1.
Temperature cut-off threshold input
Input to set maximum allowable battery
temperature. If the potential between TS
and SNS is less than the voltage at the TCO
input, then fast charge or top-off charge is ter-
Temperature sense input
Input, referenced to SNS, for an external
thermister monitoring battery temperature.
Battery voltage input
BAT is the battery voltage sense input, refer-
enced to SNS. This is created by a high-
impedance resistor-divider network con-
nected between the positive and the negative
terminals of the battery.
Charging current sense input
SNS controls the switching of MOD based on
an external sense resistor in the current
path of the battery. SNS is the reference po-
tential for both the TS and BAT pins. If
SNS is connected to VSS, then MOD switches
high at the beginning of charge and low at
the end of charge.
Charge status outputs
Push-pull outputs indicating charging
status. See Table 2.
VCC supply input
5.0V, ±10% power input.
Charge current control output
MOD is a push-pull output that is used to
control the charging current to the battery.
MOD switches high to enable charging cur-
rent to flow and low to inhibit charging
Discharge control output
Push-pull output used to control an external
transistor to discharge the battery before
Charge inhibit input
When low, the bq2004E/H suspends all
charge actions, drives all outputs to high im-
pedance, and assumes a low-power opera-
tional state. When transitioning from low to
high, a new charge cycle is started.